1. Field of the Invention
The present invention relates to a fan housing and, more particularly, to a fan housing including a plastic casing and a metal frame. The present invention also relates to a heat dissipating fan having such a fan housing.
2. Description of the Related Art
Conventional fan housings generally include a base and a lateral wall extending along an outer periphery of the base. The lateral wall includes an air inlet and an air outlet. A motor and an impeller can be mounted to the base to form a heat dissipating fan. The impeller can be driven by the motor to drive in air currents via the air inlet. The air currents exit the air outlet for heat dissipation purposes. The fan housings are generally integrally formed. As an example, the fan housings can be formed of metal, such as aluminum, by integral casting. Although the fan housings made of metal can provide reliable support for the motor and the impeller, the metal fan housings are much more expensive than those made of plastic material. However, the fan housings completely made of plastic material can not provide sufficient structural strength to support the motor and the impeller, resulting in products with poor quality.
A fan housing 9 including a metal frame 91 and a plastic casing 92, as illustrated in FIGS. 1 and 2, has been proposed to solve the disadvantages of conventional fan housings integrally formed of either metal or plastic material. The metal frame 91 includes a fixing portion 911 on an outer periphery thereof. The plastic casing 92 integrally envelopes the fixing portion 911 of the metal frame 91 by injection molding and, thus, forms a lateral wall along the outer periphery of the metal frame 91. The costs can be cut by forming the plastic casing 92 (i.e., the lateral wall) with inexpensive plastic material while the metal frame 91 provides certain structural strength. An example of such a fan housing 9 is disclosed in Taiwan Patent Publication No. 200925842.
It is not uncommon to replace the impeller with a larger or smaller size and to select a motor of an appropriate power in response to differing heat dissipation requirements. The size and shape of the fan housing must be changed accordingly. As an example, when a larger impeller is to be coupled with the same metal frame 91, a compartment defined by the plastic casing 92 formed along the outer periphery of the metal frame 91 after injection molding may be too small to receive the larger impeller. Thus, a manufacturer must prepare metal frames 91 of differing sizes and shapes for use with impellers or motors of differing sizes, resulting in inconvenience in manufacturing of molds and leading to an increase in the manufacturing costs as well as difficulties in stock management.